Refinishing of worn rolls



Sept. 21, 1965 H. PONNATH REFINISHING 0F WORN ROLLS 5 Sheets-Sheet 1Filed Feb. 2, 1962 Hons Ponnorh BY ATTORNEYS Sept. 21, 1965 H. PONNATH3,207,013

REFINISHING OF WORN ROLLS Filed Feb. 2, 1962 5 Sheets-Sheet 2 HansPonnufh BY PM W MEW; 71 a ATTORNEYS Sept. 21, 1965 H. PONNATHREFINISHING OF WORN ROLLS 5 Sheets-Sheet 3 Filed Feb. 2, 1962 lNVl-NTO/PH on 5 Po n norh BY fl w W MLW /W ATTORNEYS United States Patent3,207,013 REFINISHING 0F WORN ROLLS Hans Ponnath, Rheinhausen, Germany,assignor to Huettenund Bergwerke Rhinehausen Aktiengesellschaft, Essen,Germany, a Germancompany Filed Feb. 2, 1962, Ser. No. 170,689 5 Claims.(CI. 82-14) In the rolling of metals into rolled shapes, there areemployed rolls having grooves in the surface thereof, shaped anddimensioned to define the cross section to be given to the material tobe rolled. The rolls therefore possess along their length portions ofunlike diameter or caliber, and the trace of the surface of such a rollin a plane containing its axis may be referred to as the profile of theroll. The material to be rolled is passed through a succession of standsof such rolls having suitably graduated profiles in order to give thematerial the desired shape after the proper number of passes. Ingeneral, the profiles of these rolls are made up of straight or curvedlines of various inclinations to the roll axis, and the surface of sucha roll may be regarded as composed of surfaces of revolution generatedby these lines. These various surfaces on the rolls are subjected tounlike amounts of stress in use and therefore they wear at unlike rates.In consequence, the profiles of the rolls, and their calibers, changewith use to such an extent that the rolls finally become unuseable. Theycan however be restored to the useable condition by turning them down ina lathe. This requires removal in the turning operation of whatevermaterial is required to restore the original profile.

The amount of material which must be so removed depends upon the maximumwear which has occurred at any point on the profile of the roll. Sincegenerally each roll includes a plurality of portions of unlike diameteror caliber, the turning operation is conditioned by that portion of theroll which has undergone the most wear. That is to say, the portion ofthe roll which has undergone the most wear determines the radial extentof the cut which must be effected over the entire surface of the roll inorder to restore eits original profile.

In order to identify this region of maximum wear, it is necessary tomeasure each portion of the roll of distinct diameter and to determinefrom the measurements so made where the maximum wear has occurred. Thismeasuring operation, when performed by hand, is tedious and is subjectto error on the part of the operator. For simplicity, it has heretoforebeen customary to take only sample measurements at randomly selectedpoints and then, for the sake of safety, to increase arbitrarily theamount of the cut to be made above that indicated by the maximum amountof wear indicated by these measurements.

In this operation as heretofore performed it has been customary toemploy templates of sheet form made of steel or of synthetic material.It has been necessary for these templates to be accurately finished andaccordingly the manufacture thereof has been costly.

By means of the present invention these difficulties in the process ofreworking rolling mill rolls are overcome. By means of the presentinvention it is possible to rework such rolls with a minimum of effortand with removal of a minimum of material.

According to the present invention the roll to be reworked is firstmeasured. The results of these measurements are then recorded on asuitable record medium such as a magnetic or punched tape or the like.The measured values so recorded are then compared with datarepresentative of the desired profile, likewise recorded on a similarrecord medium, i.e., with data repre- 3,207,013 Patented Sept. 21, 1965sentative of the original profile of the roll which is to be restoredthereto by the refinishing process of the invention. The departures ofthe actual roll measurements from the intended or desired ones are thencomputed by means of a computing device. These departures are thenemployed to determine that shift of the desired values which, uponrecording on a new record medium of the desired values so shifted, willeffect such a control of the cutting tool in the turning operation as toreduce to a minimum the amount of material which must be removed fromthe roll being reworked or refinished. In the turning operation of theworn roll the cutting tool is then moved relative to the work in amanner known per se in the operation of program-controlled machinetools.

More particularly, the amount of material to be removed is reduced bydetermination, for example with the aid of a computer, of a leastmaximum difference, or amount of departure, between the desired andactual roll measurements as a function of relative axial shift of theactual and desired profile data. This least maximum difference isdetermined by effecting an axial shift of the schedules of actual anddesired diameters for the entire roll relative to each other in anamount c0rresponding to this least maximum difference.

According to a further feature of the invention, a further reduction inthe amount of material to be removed is achieved by effecting eachportion of the roll having a separate diameter or set of diameters aseparate axial displacement of the actual value diameter measurements ofthat portion with respect to the desired diameter values of that portionby an amount producing a least maximum difference between those actualdiameter measurements and those desired diameter values as so shifted.

Adjustment of the record medium bearing the data for control of thecutting tool in the lathe to the ap propriate axial displacement asdetermined by the computer can be effected by hand in a known manner.Since the rolling process requires at least two rolls, it is necessaryin each instance to determine as between the rolls which Work togetherthe one whose profile has suffered the most wear. The least maximumdeparture between the actual diameter of this roll and the diametersscheduled for it by the process of the invention serves to control thecutting tool in reworking all rolls employed in a single pass of thematerial being rolled, whether this least maximum departure is computedon the basis of a single axial shift of the complete actual and desiredroll profiles or on the basis of separate shifts for the variousportions thereof.

Further details of the invention will be explained with reference to theaccompanying drawings in which:

FIGURE 1 is a diagram illustrating control of a lathe for therefinishing of a roll, the cutting tool of the lathe being controlled bymeans of a signal representing a schedule of desired diameters recordedon a magnetic tape;

FIGURE 2 is a diagrammatic representation of a scanning device for thedetermination and recording of the extent of wear of a roll as apreliminary to its being refinished;

FIGURES 3a to 3e are curves useful in explaining the invention; and

FIG. 4 is a block diagram further illustrating that step in the processof the invention whereby there is determined the optimum axial shift ofthe desired profile before the desired profile so shifted is reworkedonto the roll; and

FIG. 5 is a block diagram illustrating the reworking of the roll to thedesired profile so axially shifted.

Referring now to FIG. 4 there is shown a block diagram of apparatus bymeans of which, from a scanning of the worn roll as in FIG. 2, there isdetermined the optimum.

axial shift of the desired profile which permitsthe roll to be reworkedto that profile with minimum radial out.

In FIG. 4 the scanner 4 mounted on carriage 13 is seen to movelongitudinally of the roll by operation of lead screw 22 andtransversely thereof by operation of crossscrew 28. The ways 24 in whichlead screw 22 is journaled and held against lengthwise motion and whichguide the carriage 26 in lengthwise motion have been omitted from FIG. 4for clarity. The scanner may be moved longitudinally at an arbitraryslow rate and the scanner 4, responding to varying contact pressuresbetween the stylus 5 and the roll, cause-s the transverse lead screwdrive motor M to execute motions as required to maintain the stylus incontact with the roll. For this purpose the scanner and the transverselead screw drive motor are connected into a conventional closed servoloop which may include an amplifier as shown at 99. The scanner 4develops electrical signals which indicate the magnitude and sign of thedeparture of the stylus from a selected contact condition with the roll(eg a particular value of stress or pressure between the stylus and theroll), and these signals are employed via the amplifier 99 to energizethe motor M in the direction and amount required to restore the stylusto proper contact with the roll, all in accordance with conventionalservo practice.

For example, the stylus 5 may be resiliently mounted by means of springs60 to possess an equilibrium position with respect to the cross-slidecarriage 13 and to be movable parallel to the cross-slide screw 28 outof that equilibrium position in response to engagement with the roll.One conventional form of apparatus for generating signals representativeof departures of the stylus from this equilibrium position is indicatedin FIG. 4. Fixed to the stylus is the primary winding 62 of atransformer energized from a suitable A.C. source, not shown. Adjacentto the primary winding 62 are two secondary windings 64 and 66, fixedwith respect to the carriage 13 and oppositely wound with respect toeach other. For the equilibrium position of the stylus, equal andopposite voltages are induced in the secondary windings 64 and 66 andthe algebraic sum thereof perceived in the servo amplifier 99 is zero.Departures of the stylus from this equilibrium position in one or theother direction will produce as the sum of the voltages in windings 64and 66 a net voltage of amplitude representative of the amount of thestylus departure from equilibrium position and having a 180 phaserelation with respect to the energizing voltage in winding 62 whichindicates the sense of the stylus departure from equilibrium position.

The transverse lead screw drive motor M develops sig nals representativeof actual cross-slide position and hence of scanner position, forexample with the aid of conventional means such as a helicalpotentiometer coupled to motor M and these signals representative ofactual crossslide position and hence of actual roll diameter aredelivered to a recording device 100 which may incorporate the magnetichead 6 of FIG. 2. There are also delivered to the recording device 100signals representative of the longitudinal position of the scanner,these signals being those by means of which the longitudinal lead screwdrive motor M is controlled for longitudinal drive of the scanner.

The data on actual roll diameters as a function of position along theroll thus recorded in the device 100 is the data of curve 7 in FIG. 3b.It is therefore a record of variations in the actual diameter of theroll, referred to the diameter of the roll at the lands thereof such as36, 38, 40 and 42. The record may take the physical form of a magnetictape as shown at 10 in FIG. 2.

A storage device 102 contains a record of desired diameters, again as afunction of position along the roll. The data on the record in device102 is the data of curve 2 as shown in FIG. 3a and constitutes thereforea record of the desired variations in the diameter of the roll, referredto the diameter thereof at the lands 36, 38, 40 and 42.

Acomputer 104, which may be conventional in nature and of either analogor digital type, operating on the data recorded in device 100 and on thedata recorded in device 102, subtracts the ordinates of curve 2 in FIG.So from the corresponding ordinates of curve 7 in FIG. 311. Moreparticularly, the computer 104 performs this subtraction for each of aplurality of relative axial, positions of the curves 3a and 3b,selecting that relative axial position for which the differences exhibitthe least maximum value. Determination of this axial shift giving leastmaximum difference is readily performed since with conventionalapparatus the taking of the differences for a single axial shiftrequires only a very short instant of time..

Referring now to FIG. 5, there is shown a signal generating device 108which contains a program of the desired r-oll diameters, and moreparticularly a program. of the desired variation in roll diametersreferred to the lands on the desired roll surface, this program ofdesired roll diameters being axially shifted with reference to theposition ,of that program as shown in FIG. 3a by the axial shift whichhas been determined in accordance with the operations described inconjunction with FIG. 4. The device 108 delivers this program of axiallyshifted desired diameters to the cross-slide drive motor M andsimultaneously it delivers to the longitudinal lead screw drive motor Msignals representative of the successive axial positions to which thecross-slide positions so delivered to M correspond. In this way thecutting tool of FIG. 5 is caused to rework the roll to its originalprofile, with minimum radial cut by virtue of an axial shift of thedesired profile, all in accordance with the invention.

For the refinishing of a roll according to the invention, it is firstnecessary to compare the original profile of the roll with that of theroll as worn.

In order to record the actual profile there may be employed, asindicated in FIGURE 2, a scanning device 4 mounted on the cross slide 13of a lathe whose ways are shown at 24. The scanning device 4 may beelectric or electronic in nature. The stylus 5 of the device 4 executesa motion, composed of very small steps, which closely follows the actualprofile of the roll 20. From this motion the device 4 develops signalscorresponding to the profile of the roll, of varying duration, which aretransmitted to the lead screw 22 for lengthwise motion of the carriage26 and to the cross screw 28 for motion of the cross slide 13. Thisprocess corresponds to the scanning of a template or of a sample in acopying lathe. Axial motion of the scanner is effected by means of amotor M operating on the lead screw of the lathe, and cross motion iseffected by means of a motor M operating on the cross screw.

The motions of the lead screw and cross screw are communicated to astorage device, for example via a magnetic recording head 6 and arerecorded on a magnetic tape 10 or other suitable record medium of thestorage device. The record may be in either digital or analog form. Atwo-dimensional graphic representation of this record has beensuperposed on the tape 10 in FIGURE 2 in the form of the curve 7 whichis drawn with reference to axes of ordinates and of a-bscissae y and x.The axis y represents inverse radial position from the axis of the roll20 and the x axis represents axial position lengthwise of the axis ofthe roll. That is, increasing values of y represent positions closer tothe roll axis. In similar fashion there is recorded on the same recordmedium i.e. on the tape 10 (for example in a separate track thereon) aset of signals representative of the desired roll profile. This desiredprofile is shown in the two-dimensional graphic representation of FIGURE2 at the dash line curve 2.

the tape in FIG. 2. In FIGURE 3a, the curve 2 repre sents the desiredprofile for the roll, i.e. that which it possessed when new, whereas inFIGURE 3b the curve 2 has superposed thereon the curve 7 representativeof actual roll profile.

The difference y y represents the amount of wear which the roll hasundergone, measured radially, and this difference is plotted in FIGUREas a function of axial position x lengthwise of the roll, where it isseen to have a maximum value indicated at 9. If the roll were to beturned down without axial displacement of the profile, it would have tobe turned to reduce its radius throughout its length by the amount 9from the original value of that radius in order to restore the originalprofile. This is illustrated in FIGURE 3d, where a radial displacementof the amount 9 between the curve 2 representing the original profileand the curve 12 representing the desired profile is seen to be justsufficient to provide clearance between the actual profile 7 and areproduction, as at 12, of the original profile.

In accordance with the invention instead, the intended profile indicatedat 12 in FIGURE 3d is subjected in the computer to an axial shift x to anew position indicated at 12a. As a result of this shift the maximumradial separation of the actual profile 7 from the intended profile 12a(which is a reproduction of the original profile 2) is reduced from theamount 9 to the amount 9a. This shift is effected in the computingmachine and the curve 12a thus obtained serves to control the cuttingtool in the tuming operation by which the roll is reworked. That is, thecurve 12a represents the profile which the cutting tool imparts to theroll in the refinishing process of the invention. It is to be emphasizedthat the data representative of the actual and desired profiles need notbe stored in the form of a curve. Representation thereof in the form ofcurve has been employed only for the sake of clarity. The mode ofstorage and of computing are dependent on the nature of the computeremployed.

In the modification of the invention illustrated in FIG- URE Be there iscomputed for each portion of the roll having a distinct diameter or setof diameters such an axial shift of the actual and desired profiles ofthat portion with respect to each other as to result in a least maximumradial separation of the actual and desired profiles for that portion.The largest of these least maximum values may then be selected tospecify the reduction be ow the original profile radius to be effectedover the whole length of the roll in refinishing it.

More particularly it will be observed that the profile of FIGURE 3acomprises three portions 30, 32 and 34 limited by lands 36, 38, 40 and42 on the surface of the roll. No rolling action takes place at theselands, as indicated by the absence of wear there in FIGURE 3b. In otherwords, the curves 2 and 7 of FIGURE 3b coincide at these lands.Consequently, the curve 8 of FIGURE 30 is made up of three parts, 44, 46and 48 of non-zero value. Curves 44, 46 and 48 are plots of the wear atroll portions 30, 32 and 34 respectively, and each has a separatemaximum. These maxima are shown at 33, 9 and respectively. As alreadystated, if the roll is to be refinished with its profile 2 in the sameaxial position on the roll as originally, the turning operation willhave to reduce the radius of the roll everywhere by the amount 9 belowthe original radius value. If, in accordance with the method of theinvention explained in connection with FIGURE 3d, the entire schedule ofdesired diameters represented by curve 2 or 12 in FIGURES 3a or 3d isshifted as a unit with respect to the schedule of actual diametersrepresented by curve 7 in FIGURE 3b, the curve 8 of FIGURE 3c will have,for such an axial shift in the amount x a different shape whose maximumordinate is the amount 9a of FIGURE 3d, and this maximum is less thanthe maximum assumed by the curve 8 (of altered shape) for any otheraxial displacement of the curves 2 and 7.

In accordance with the particular form of the method of the inventionillustrated in FIGURE 3e, the roll is refinished with the profileportions 30, 32 and 34 in altered relative axial positions, with aseparate axial shift for each, and the radial cut made in therefinishing operation is determined as the largest of the least maximafound for curves 44, 46 and 48 individually by axially shiftingseparately the schedules of diameters for profile portions 30, 32 and 34with respect to the schedules of measured diameters of those portionsrespectively.

For the portion 30, the least maximum ordinate of curve 44 occurs withan axial shift as indicated at 17 in FIGURE 3e; for portion 32 the leastmaximum ordinate of curve 46 occurs with axial shift 16, and for portion34 the least maximum ordinate of curve 48 occurs with still anotheraxial shift 19 of portion 34. The largest of these three least maxima isindicated at 18, which, it will be observed, is substantially less thanthe amount 9a of FIGURE 3d. The roll is refinished to possess theprofile 15 of FIGURE 3e which represents the profiles of the threeportions 30, 32 and 34 of FIGURE 3:: shifted axially with respect totheir original positions (shown in FIGURE 3a) by the amounts 17, 16 and19 respectively and all shifted radially by the amount 18.

Thus the plural axial shifts effected in the method according to FIGURE3e provide a further means of reducing the amount of material to beremoved in refinishing the roll.

FIGURE 1 shows schematically how the roll is turned in accordance withthe data so derived. In FIGURE 1, reference character 1 identifies astorage device in which are recorded the data 12a or 15, according asthe roll 20 is to be refinished in accordance with the method describedin connection with FIGURE 3d or in accordance with that described inconnection with FIGURE 3e. This data is scanned from the record medium 1by means of a scanning device 3. Control signals developed in thescanner are delivered to the lengthwise and transverse lathe carriagedrives M and M for positioning of the tool support 13 and its cuttingtool 14 with respect to the roll 20, which is mounted between the livecenter in the headstock and the dead center in the tailstock (not shown)of the lathe. In FIGURE 2 the roll 20 is also to be understood asmounted between the centers of the lathe.

The invention thus permits reworking of rolling mill rolls with aminimum of cutting.

While the invention has been described in terms of the refinishing ofrolls to restore their original profiles thereto, it is not necessarythat the profiles to which the rolls are refinished be the same as thatoriginally present thereon.

I claim:

1. A process of refinishing a roll comprising the steps of measuring thediameter of the roll as a function of position along its length,recording the measured diameters on a record medium, recording on arecord medium the desired diameters to which the roll is to berefinished, determining as a function of relative axial postion of saidrecorded measured and desired diameters the least maximum differencebetween said recorded measured and desired diameters, and turning saidroll to a profile defined by said desired diameters axially shiftedrelative to the profile defined by said measured diameters in an amountcorresponding to said least maximum difference.

2. A process of refinishing a roll comprising the steps of measuring thediameter of the roll as a function of position along its length,recording the variations in measured diameters on a record medium,recording on a record medium the variations in desired diameters towhich the roll is to be refinished, determining as a function ofrelative axial position of said recorded variations in measured anddesired diameters the least maximum difference between said recordedvariations in measured and desireddiameters with an assumedarbitraryradial relation between said measured and desired diametersrepresentative of lands on a common cylindrical surface on said roll,and turning said roll to a profile defined by said desired diametersaxially shifted relative to the profile defined by said measureddiameters in an amount corresponding to said least maximum differenceand radially shifted in the amount of said least maximum difference.

3. A process of refinishing a roll including a plurality of groovesseparated by lands disposed on a common cylindrical surface, said methodcomprising the steps of measuring the diameter of the roll as a functionof position along its length, recording on a record medium thedepartures of said diameters from the diameter of said surface,recording on a record medium the departures in diameter from saidsurface desired to be imparted to said grooves in refinishing the roll,determining as a function of relative axial position of the saidrecorded measured and desired departures of said grooves collectivelythe least maximum difference between said recorded measured and desireddepartures, and turning said roll to a profile defined by said desireddepartures axially positioned with respect to said measured departuresat the position corresponding to said least maximum difference andradially positioned at a location displaced toward the axis of the rollby the amount of said least maximum difference.

4. A process of refinishing a roll including a plurality of groovesseparated by lands disposed on a common cylindrical surface, said methodcomprising the steps of measuring the diameter of the roll as a functionof position along its length, recording on a record medium thedepartures of said diameters from the diameter of said surface,recording on a record medium the departures in diameter from saidsurface desired to be imparted to said grooves in refinishing the roll,determining for each of said grooves as a function of relative axialposition of the said recorded measured and desired departures of saidgrooves individually the least maximum differences between said recordedmeasured and desired departures of said grooves individually, andturning said roll to a profile defined for each of said grooves by thesaid desired departures thereof individually axially positioned withrespect to the said measured departures thereof individually at thepositions corresponding to the corresponding ones of said least maximumdifferences and radially positioned for all of said grooves at alocation displaced toward the axis of the roll by the amount of thelargest of said least maximum differences.

5. A method of refinishing a roll having lands and worn grooves, saidmethod comprising the steps of measuring the actual variations indiameter of said roll referred to the diameter thereof at said lands asa function of position along the length of said roll, recording saidactual variations on a record medium, recording on a record medium thedesired variations in the diameter of said roll referred to the diameterthereof at said lands as a function of position along the length of saidroll, determining as a function of relative axial position of saidactual and desired variations the, least maximum difference between saidactual and desired variations, and turning said roll to the profiledefined by said desired variations at the axial position for saidprofile corresponding, to said least maximum difference.

References Cited by the Examiner FOREIGN PATENTS 1,114,501 12/55 France.1,238,963 7/60 France.

921,791 12/54 Germany.

WILLIAM W. DYER, JR., Primary Examiner.

LEON PEAR, Examiner.

1. A PROCESS OF REFINISHING A ROLL COMPRISING THE STEPS OF MEASURING THEDIAMETER OF THE ROLL AS A FUNCTION OF POSITION ALONG ITS LENGTH,RECORDING THE MEASURED DIAMETERS ON A RECORD MEDIUM, RECORDING ON ARECORD MEDIUM THE DESIRED DIAMETERS TO WHICH THE ROLL IS TO BEREFINISHED, DETERMINING AS A FUNCTION OF RELATIVE AXIAL POSITION OF SAIDRECORDED MEASURED AND DESIRED DIAMETERS THE LAST MAXIMUM DIFFERENCEBETWEEN SAID RECORDED MEASURED AND DESIRED DIAMETERS, AND TURNING SAIDROLL TO A PROFILE